Process for the refining of cracked hydrocarbon distillates



Patented Sept. 3, 1935 STT S A'iENT QFFlQE- PROCESS FOR THE REFINING OF CRACKED HYDROCAREON DISTILLATES Dakota No Drawing. Application December 5, 1931, Serial No. 579,346. Renewed March 6, 1934 3 Claims.

This invention relates to the treatment of hydrocarbon oils and refers more particularly to the treatment of the lighter distillates produced in the cracking of relatively high boiling hy- 5 drocarbon oils.

More specifically the invention contemplates the provision of a process whereby the quality of motor fuel fractions obtained by the conversion of such heavy hydrocarbon oils at elevated 1 temperatures and pressures may be improved to a point consistent with commercial motor fuel requirements, and more particularly the process aims to produce hydrocarbon distillates which are substantially free from objectionable substances such as gum-forming constituents, sulphur compounds and the like.

Certain undesirable properties are inherent in the raw motor fuel fractions resulting from the pyrolysis of heavy hydrocarbons, these being due to the presence of an excessive amount of unsaturated hydrocarbon compounds and also to the presence of sulphur derivatives of many types. While the unsaturated compounds, which include not only the olefinic but also the aromatic serise, have greater value than the straight-chain paraffin hydrocarbons in reducing the knocking tendency of motor fuels, the compounds whose unsaturation is characterized by double and triple linkages are unstable and tend to polymerize and deposit gums and resins which render the fuel nonhomogeneous on storage and develop color and odor to an undesirable extent.

While many types of treatment have been applied in attempts to remove the more unstable unsaturated compounds and retain the more stable mono olefins which contribute to the antiknock value of the fuel, relatively few have attained a commercial status because of factors such as cost of reagents, corrosion tendency and certain inherent difficulties of operation. The process comprised Within the present invention offers a solution of the problem of selective removal of the more readily reactive gum-forming unsaturated hydrocarbons and possesses many advantages over treatments at present employed for the same purpose, such as cheapness and availability of materials and simplicity and flexibility of operation from a refinery standpoint.

In one specific embodiment the invention comprises treating cracked hydrocarbon distillates in the liquid phase with hydrochloric acid containing ferric sulfate dissolved therein.

The process of the invention is particularly directed to the treatment of cracked hydrocarbon range in the liquid phase, and in practice any suitable type of equipment may be employed which will insure good contact between the reagents and the distillates. The standardized cone-bottomed agitator used extensively in all 5 refineries is readily adaptable, the reagents characteristic of the invention being added gradually during circulation of the oil from the bottom of the cone back into the top until the desired amount has been added and the desired treat- 10 ing effect is produced. In such operations the combined reagent and oil will be taken by the circulating pump which is usually of the centrifugal type and intimately mixed by the churning action of the impellers. Furthermore, the 15 pump may discharge into a line containing baffling material such as a succession of orifices or perforated plates, etc. so that thorough mixing is assured.

Reagents may be added at selected points along 20 the flow of oil through continuous treating plants, which consist in general of pumps, mixing devices for oil and treating materials, settlers, Wash tanks, etc., the reagent being conveniently introduced on the suction side of a pump which 25 discharges through mixers containing bafliing material such as vanes or successive orifies.

While it is frequently possible to treat cracked distillates sufiiciently at ordinary temperatures so that their rerunning may produce a substan- 30 tially finished gasoline except for neutralizing steps it is also within the scope of the invention to employ superatmospheric temperatures, with corresponding pressures necessary to maintain substantially liquid phase in the oils undergoing 35 treatment. The treatments may also be conducted under refluxing conditions in lieu of the use of pressure.

While the treatments characteristic of the present invention are frequently sufiicient for improving the quality of the oils to a marketable degree the process may be employed if desired as a step in combined treatments embodying other reagents such as the commonly used commercial sulfuric acid, caustic soda, fullers earth, etc., the proportions of each type of reagent being ad justed to obtain the best results.

While the temperatures employed in the treatments may vary over a considerable range, un- 50 usually high temperatures are not generally contemplated and at the most, temperatures employed will be only moderately superatmospheric up to, for example, 200 F. which will cover most instances of operation unless excessive superatmospheric pressures such as obtain in some cracking processes are used.

Judging from the results of numerous treatments upon a variety of cracked distillates, the

treating effects obtained are evidently to be explained upon the basis of selectively controlled polymerization although some efiect has been noticed upon the total sulphur content. It has been found that the compound treating reagents produce effects greater than those possible by the use of the reagents 'singly or in combination.

While numerous examples might be given of improved results obtained by the treatment of cracked distillates, it will sufiice for illustrative purposes to give one which is characteristic of the invention. The distillate treated in both cases was produced by the cracking of a heavy California charging stock, its properties being shown in the appended tabulation along with the properties of a gasoline distilled from it to make an approximately 410 end point gasoline. It will be seen that the eifect of distillation upon the sulphur content was practically negligible, that the gums as determined by the copper dish method were practically the same as in the raw distillate. within the error of the method of the determination, and that while the color was improved it was still far below that required in commercial gasolines.

The distillate was agitated under atmospheric temperature and pressure with a mixture of hydrated ferric sulfate and concentrated commercial hydrochloric acid, the former being used at the rate of 3.4 lbs. per bbl. of oil and the latter at the rate of 4.8 lbs. per bbl. of oil. A three-layer system is formed, the upper being treated oil, the intermediate a sludge of nondetermined properties and the lower layer consisting of spent reagent which may be further utilized by the addition of more hydrochloric acid. After washing the oil layer with water and rerunning'with fire and steam, agasoline was produced which had the same end point as the product from the untreated distillate, a color of 28 on the Saybolt scale and approximately 15 mgs. of gum per 100 cc. by the copper dish method. The sulphur was also reduced slightly.

Caustic washing was all that was required to render the distilled gasoline color stable when exposed to the sun in the standard 4 oz. sample bottle test for a period of 4 hrs.

Increasing the temperature by heating the distillate under. a relatively low superatmospheric pressure with the reagent, subsequently separate ing the sludge and the treated distillate, neutralizing and rerunning the latter also gave good results.

While the foregoing description and example have served todescribe and illustrate the process of the invention, it is not intended that the specification be construed in a limiting sense as the process is one of great flexibility and Wide application.

We claim as our invention: g

1. A process for the refining of cracked hydrocarbon distillates of motor fuel boiling range which comprises subjecting such distillates while in substantially liquid condition to the action' of hydrochloric acid containing ferric sulphate dissolved therein.

2. A process for the refining of cracked hydrocarbon distillates of motor fuel boiling range which comprises subjecting such oils at elevated temperatures but still in substantially liquid condition to the action of hydrochloric acid containing ferric sulphate dissolved therein.

3. A process for the refining of cracked hydrocarbon distillates of motor fuel boiling range which comprises subjecting such distillates to the action of hydrochloric acid containing ferric sulphate dissolved therein.

WAYNE L. BENEDICT. CHARLES WIRTH III. 

